Processing and Pretreatment Effects on Vanadium Transport in Nafion Membranes. Issue 1 (13th October 2015) - Xie, Wei
Abstract : This work describes how manufacturing processes and pretreatments affect the proton conductivity and vanadyl permeability of Nafion ® and how these properties are altered by running in a cell. Five Nafion membranes were examined: reinforced XL100, dispersion cast NR211 and NR212, and extruded N115 and N117. The membranes were subjected to pretreatments that included annealing at 120°C and immersing in ambient temperature and boiling water and sulfuric acid. Vanadyl permeability varied by ∼15X with pretreatment and ∼3X with manufacturing process. Variations in ionic conductivity were comparatively modest: ∼1.5X with pretreatment and ∼1.2X with processing. Differences in permeability can be eliminated by annealing the extruded membranes above their glass-transition temperature or by immersing in boiling sulfuric acid. The differences induced by processing and pretreatments were largely absent from membranes removed from vanadium redox cells subjected to repeated charge/discharge cycles.